My 454 Rebuild

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Spareparts

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I think i might have discovered the problem (fingers crossed)
When i measured the cats with a temp gun the temps were the same on the inlet and outlet of both converters.
The outlet should be a lot hotter than the inlet or they are not doing their job and could even be clogged.
Tomorrow i will find out for sure. I'll do an exhaust back pressure test and remeasure the exhaust temps at the cats again.

If they are bad and clogged I'll get some high flow cats ordered but till they arrive what can i do?
I'm thinking i can unhook the rear o2 sensors and rod out the cat's and i should be good for a week or so till i can have the exhaust system redone.
I know ill have a CEL but no cats and no rear o2 sensors should not affect driveability if i understand things right?
Near the end he explains it as do several other videos.
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BeXtreme

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I think i might have discovered the problem (fingers crossed)
When i measured the cats with a temp gun the temps were the same on the inlet and outlet of both converters.
The outlet should be a lot hotter than the inlet or they are not doing their job and could even be clogged.
Tomorrow i will find out for sure. I'll do an exhaust back pressure test and remeasure the exhaust temps at the cats again.

If they are bad and clogged I'll get some high flow cats ordered but till they arrive what can i do?
I'm thinking i can unhook the rear o2 sensors and rod out the cat's and i should be good for a week or so till i can have the exhaust system redone.
I know ill have a CEL but no cats and no rear o2 sensors should not affect driveability if i understand things right?
Near the end he explains it as do several other videos.
xc_hide_links_from_guests_guests_error_hide_media
I was going to say this after seeing your post about them being the same temp. A properly catalyzing element will increase the temp at the outlet of the catalytic converter. That doesn't mean they are clogged, but it could be. That also doesn't necessarily cause the engine to think it is too rich and pull the LTFTs down, but maybe it could. I would suggest maybe just pulling your y-pipe off and look at them from the front, you will likely be able to see if they are clogged.

You can recycle your stock cats for about $500-600, so I wouldn't just rod them out to drive around for a week until you can replace them.
 

Spareparts

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Well i pressure checked the cats and they are not plugged so back to the drawing board.
I notice at idle in park it says my engine in at 3.5X% load. Seems high? What could be causing that if it is?
 

Spareparts

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So here is what i have done this morning.
Check back pressure at the cats. Reads maybe 1/2 lb up to 3000 rpm so they should not be a problem in that respect.
Someone suggested switching back to the 0411 as that might help diagnose as it can show more parameters. So i now have the 0411 back installed.
Curious though. I have the rear o2 sensors unplugged but i still have LTFT readings with the old black box ECU and the 0411 ECU. That seems strange to me as the 0411 has the rear o2 sensors disabled.
I was under the assumption that LTFT was a function of the rear o2 sensors and disabled in the tune and unhooked they should be reading/doing nothing? but,
The LTFT seem to be coming down but it's really to soon to tell as i have only went about 5 miles.
Truck is for sure idling smoother but still a little rough. Instant fuel mileage reading in Torque has jumped from 9mpg(ish) to 14mpg(ish)
 

BeXtreme

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So here is what i have done this morning.
Check back pressure at the cats. Reads maybe 1/2 lb up to 3000 rpm so they should not be a problem in that respect.
Someone suggested switching back to the 0411 as that might help diagnose as it can show more parameters. So i now have the 0411 back installed.
Curious though. I have the rear o2 sensors unplugged but i still have LTFT readings with the old black box ECU and the 0411 ECU. That seems strange to me as the 0411 has the rear o2 sensors disabled.
I was under the assumption that LTFT was a function of the rear o2 sensors and disabled in the tune and unhooked they should be reading/doing nothing? but,
The LTFT seem to be coming down but it's really to soon to tell as i have only went about 5 miles.
Truck is for sure idling smoother but still a little rough. Instant fuel mileage reading in Torque has jumped from 9mpg(ish) to 14mpg(ish)
LTFT has nothing to do with the rear O2 sensors. The rear O2 sensors are only there to determine cat function for emissions. All fuel trim adjustment happens based on the front O2 sensors.
 

Spareparts

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Just thinking here but im wondering something.
If the O2 sensors are not getting the power or ground for the head to work could that cause the negative fuel trims?
 

BeXtreme

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Just thinking here but im wondering something.
If the O2 sensors are not getting the power or ground for the head to work could that cause the negative fuel trims?
If there was a short or open you would get a code. If there was no power to the O2 sensor you would get a code. A lack of power to the heating element would just cause it to be slow to come up to temp and would maybe cause slower reactions at warmup. I don't think that is the issue though since it seems to be cycling across stoich at the expected rate.
 

Spareparts

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Ok, thanks for the info @BeXtreme

Here is something else i tried today.
Truck was warm. Turned it off and unplugged the MAF and truck ran WAY better and fuel trims looked normal after a short 1 mile drive. Almost running perfect but not quit.
I'm letting the fuel trims reset and will try a little longer drive and see what happens.
BTW the CEL is off with the MAF unplugged. I believe Black Bear has turned off most of the CEL codes. I can email someone the bin if they would like to look,

I have 2 MAF one new and a old used one and they both read nearly the same.

Knowing this from what i understand it is almost guaranteed i have a vacuum leak. Bummer is the only place it could be is under side of the intake or the EGR valve.
I have tried 2 EGR valves with neither making a difference already though.
 

Spareparts

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Plugged off the EGR and made no difference.
If i unplug the PCV and plug the breather and shoot starting fluid into the oil fill tube it makes no difference If i plug the pvc hole and breather pressure builds at the oil fill tube.
I do not have a intake leak for sure or any vacuum leak.
I'm beginning to think i have some weird electrical problem.
Might be a ignition problem but i have used two different caps and rotors. two new sets of wires, Different coil and ICM.
Distributor has a new gear and CMP is -0.3ish and fairly steady sometimes showing +0.3ish and shaft had no free play when i installed the new gear but maybe there was play i did not notice.
Spark plugs are new installed last weekend.
Compression is even between 155 and 160psi.
Vacuum gauge reads 19inhg.
I went ahead and checked for 12V at the rear o2 sensor with a test light and there was nothing but engine was 160F so maybe the ECU turns it off.
Ill check again in the Am when it is cold before starting.
 
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